The present invention generally relates to semiconductor processing and, in particular, to methods and systems for managing fluctuations in power supplied to an apparatus employed for semiconductor processing.
A variety of semiconductor processing applications, such as ion implantation, plasma etching or plasma-enhanced chemical vapor deposition (PECVD), are known. Proper performance of such semiconductor processing applications depend, as least in part, on stability of one or more operational parameters during a processing session, e.g., the vacuum level, deposition rate, temperature or implant dosage. The stability of the operational parameters can in turn depend on stability of power/voltage applied to an apparatus employed for performing the process.
Although the occurrence of a power fluctuation event during almost any semiconductor processing session can be harmful, it can be particularly damaging to ion implantation. Ion implanters are routinely utilized to implant ions in semiconductor wafers. Such implanters typically include an evacuated housing maintained at a low pressure, an ion source that generates a plurality of ions, extraction electrodes coupled to the ion source for extracting ions therefrom to form an ion beam, and one or more magnets that allow selecting ions having an energy in a desired range and steering them to a substrate. The proper functioning of these and other elements of an ion implanter depends, at least in part, on the stability of the power/voltage supplied thereto. For example, a drop in the voltage provided to the magnet can lead to an undesired change in the trajectory of the ion beam, which can in turn result in degradation of the wafers as well as contamination of the implanter's housing. Such fluctuations of the power can occur, for example, when the line voltage drops temporarily below its normal value, a condition commonly referred to as a “power sag.”
One possible way of compensating for such power fluctuations is to equip the implanter with backup power storage devices, such as, capacitors or batteries, that can be activated in the event of a power drop to maintain the supplied power at an acceptable level. However, an ion implanter typically requires a significant amount of power. Hence, such a compensation scheme would typically necessitate a large number of capacitors and/or batteries, with their concomitant costs. Further, in some extreme cases, the duration of a power fluctuation event may be so long as to exhaust the energy storage capacity of such installed backup devices. Although larger capacitive devices can help ride out longer power fluctuations, all “back-up power” systems are limited and, once their capabilities are exceeded, they provide limited (if any at all) protection for wafers undergoing ion implantation at the time of the power fluctuation.
Accordingly, there is a need for new methods and systems for managing fluctuations of power supplied to semiconductor processing equipment.
There is also a need for such methods and systems for managing fluctuations of power supplied to an ion implanter, especially during semiconductor processing.